Relays and fuses replaced. We've just had a run and she stalled at 65 degC with the lambda volts falling from 950 mV to 25 mV. The battery is only a month old with good voltage (12.6v with ignition on, not running - and charging at 14.2v at idle. I've just checked the resistance of the stator windings and they are all around 0.6 to 0.7 ohms. I tried to start the engine with the lambda probe disconnected and she will not catch. It's a pity that I cant "rewind" the IDiag trace to study the various relationships a bit more closely.
Stator windings good hot or cold ( 0.8 ish ohms), and infinite resistance to earth. Had another run in the garage, and at around 50 degC the lambda mV drops and main voltage drops to 12v and the engine stops with no faults showing. I am suspecting the lambda probe so I unplug it and still the bike will not run ?? Crank position sensor loom plug is spotless. I think that I will take the gen cover off and have a butchers unless anyone has got any other ideas ??
if you want to rule out the lambda altogether, its possible to disable it in the ECU (after making a backup) with the cable you have and some additional software you could also check the a/c output voltages from the stator when you get the engine running again loneelec sell a bluetooth ODB dongle for £15 you can use with android devices running scanm5x for real time data logging ifyou want to go down that route.
Cheers funkatronic but I am about at my limit with IT stuff, but I might buy this of ebay :- Oxygen lambda o2 sensor eliminator kit Ducati Monster S2R 1000 800 S4R 695 Am I OK running the engine with the alt unplugged _ must be or you would'nt have suggested it !! I guess that I check the voltage between each yellow wire and earth ?
I don't think your lambda probe is the issue - I think the voltage is dropping too low to the ECU, which then is switching off and so isn't sending any current to the Lambda. You could take off the generator cover but that might not tell you much more than the readings you've taken already unless the stator is deep fried. With the yellow wires' connector disconnected, with the engine running, you should see the same AC voltage on each of the phases of the alternator - my ST4s manual says 27±10V @ 2000RPM, 78V±6000RPM. The other component I'd be looking at is the regulator/rectifier. Any signs of burning/high resistance on the connector for the 3 x yellow wires coming from the stator? Does the reg/rec have a good contact with the frame? Do you see good continuity between the Red and Black wires and battery voltage/ground as necessary?
If the battery volts drops to 12V then it has stopped charging. Have you considered that the regulator may be faulty? The voltage isn't going to drop like that for any other reason except perhaps a heavy electrical load which is very unlikely. Your measurement of the stator resistance sounds about right. There should also be no continuity between any of the 3 yellow wires and ground. With the regulator disconnected you should see about 30V across any two of the yellow alternator wires at around 2,000 rpm. Do not rev the engine too high when checking this or the high voltage generated within the stator windings can flash over damaging the insulation. Also, Lambda output should be 1.00V or very close to it. If it is dropping to 0.25mV no wonder the bike won't idle. Is the Lambda supply voltage stable? This derived from the ECU which, as @finm has said, is itself susceptible to low voltages.
I hope a replacement regulator sort it for you. I'd seen this thread for a while but hadn't paid much attention. Then when I did it's interesting how @Turbogeek and myself came to the same conclusion almost simultaneously.
She has a new regulator and battery. I checked the diodes on the old reg and they were all good. I have run a separate earth to the reg/rec but the bike wont start now until she cools right down - the alt output test will get me away from Strictly which is always a good thing !! Previously the battery voltage was 14.2v on idle - until it got warm !! It must be the alt I guess ??
As I said, I hadn't paying much attention to this thread. Since it is a new regulator and battery it could well be the stator. Check the resistance to ground that I mentioned above. It should be infinite or at least many Megohms.
im happy to help you diasble the lambda if you want but others have said it seems unlikely to be the root cause, and the bike should run without it connected a voltage drop switching the ecu off would make sense. it would also explain lack of errors logged in diagnostics
Cheers Derek, all infinite and I'll check output when I can get the beggar to start. Battery voltage 13.v with ignition off, drops to a smidge under 12 volts when starter pressed so that is about right. Cheers too funkatronic !
Keep charging the battery in between goes. You got to 90°c before you ran out of electricity last time.
I just managed to get a reading from the alt, around 15v AC on each of the yellow wires to earth, didnt get chance to measure across two yellows - she only ran for two mins max. The early test runs, maybe a week ago, got the engine temp up to 90 degC, that then dropped to only getting to 60 deg, then 40, and just now she only ran for two mins. As the alternator was disconnected during this run - can it be a likely candidate for my woes ??
Of course !! But I get infinity, with engine not running, between yellow and ground so it means that - um ?? Anyway, I will take the cover off tomorrow and take a look - looks like we are nearly there. Again, many thanks for everyone's help - will keep you posted
Just found, at Wemoto, an Electrex stator for £90 - sounds good. Electrex are a good make I believe ?
